ViewBag, ViewData, TempData, Session - how and when to use them?

Question

ViewData and ViewBag allows you to access any data in view that was passed from controller.

The main difference between those two is the way you are accessing the data.

Answer 1

ViewBag, ViewData, TempData, Session - how and when to use them?

ViewBag

Avoid it. Use a view model when you can.

The reason is that when you use dynamic properties you will not get compilation errors. It's really easy to change a property name by accident or by purpose and then forget to update all usages.

If you use a ViewModel you won't have that problem. A view model also moves the responsibility of adapting the "M" (i.e. business entities) in MVC from the controller and the view to the ViewModel, thus you get cleaner code with clear responsibilities.

Action

public ActionResult Index()
{
    ViewBag.SomeProperty = "Hello";
    return View();
}

View (razor syntax)

@ViewBag.SomeProperty

ViewData

Avoit it. Use a view model when you can. Same reason as for ViewBag.

Action

public ActionResult Index()
{
    ViewData["SomeProperty"] = "Hello";
    return View();
}

View (razor syntax):

@ViewData["SomeProperty"]

Temp data

Everything that you store in TempData will stay in tempdata until you read it, no matter if there are one or several HTTP requests in between.

Actions

public ActionResult Index()
{
    TempData["SomeName"] = "Hello";
    return RedirectToAction("Details");
}


public ActionResult Details()
{
    var someName = TempData["SomeName"];
}